More specifically the invention refers to a roller blind structure comprising cylindrical member having secured thereto one end of a screen and being rotatably mounted in two axially spaced apart brackets and being further provided with a pulley to the hub of which is secured one end of a cord, said cord being intended to be wound upon said hub in a direction opposite to the direction in which said screen is wound upon said cylindrical member, such that unwinding cord from said pulley results in said screen being wound upon said cylindrical member and vice versa.